The primary goal of this project is to extend ongoing efforts to study, expand and improve early intervention strategies aimed at ameliorating aggressive and antisocial behavior in young boys who are at risk for subsequent maladjustment. Two viable but divergent approaches, namely family-based intervention and child-based cognitive-behavioral intervention, will be evaluated separately and jointly in a treatment outcome study with 120 markedly aggressive and oppositional boys ages 5 to 9 years. A family-based treatment that controls for positive contact between a staff member and the child is also included in the design to rule out nonspecific effects of child involvement in treatment. Outcome measures assessed at pre-treatment, post-treatment, and nine-month followup include teacher and parental measures of aggression, general social adjustment, and related behavior problems, measures of cognitive and problem-solving behaviors, observation of parent-child interaction, and assessment of parental improvement. The experimental design includes stratified random assignment to treatment conditions, conditions counterbalanced across six therapists, and assessment of treatment fidelity to verify the independent variable. A second goal of the study is to characterize the effect of child involvement on parental engagement in the family-based treatment. The family-based treatment emphasizes social learning principles and applications, active parental intervention to promote positive child behaviors, and an expectation-enhancing treatment regimen that expands therapy discussions to include topics outside of child behavior. The primary measures of parental engagement include a systematic therapy- session observation code (Therapy Process Code) to assess parental resistance and therapist behaviors, parental measures of consumer satisfaction, and participation variables pertaining to completion of therapy assignments, appointments kept, and punctuality of attendance. Achievement of the two goals of the study will provide additional understanding of treatment effectiveness as well as clues about overcoming engagement obstacles.